Scavenging for two-stroke cycle engines



P 7, 1948. H. T'. PYK ET AL SCAVENGING FOR TWO STROKE CYCLE ENGINES 2 Sheets-Sheet 1 M H W H mmn u H HM... M W WHWHmm n M hu 5 HP m v x V I V. H 4 4\W k V 2 2 A 27, 1948. H. 'r. PYK ET AL 2.4401545 SCAVENGING FOR TWQ STROKE CYCLE ENGINES 2 Sheets-Sheet 2 Filed Oct. 6, 1945 FIG] Ill

Patented Apr. 1948 UNITED STATE s PATENT-f OFFICE schvsneme ron 'rwo-s'rnoxa crops Exams Herman i Theodor l'yk, Saltsio-Duvnas, and Hild- Gunnar Gamner, Btorangen, Sweden, as-

slgnors to Aktiebolaget Atlas Diesel, Sickla,

near Stockholm, Sweden, a

. Sweden Application April 6, 1945, Serial No. 586,918

In Sweden April 18, 1944 '1' cam. (01. 123-65) the combustion cylinders in engines with doublefiow as well as'uniflow scavenging.

For this and other purposes we provide in a two stroke cycle internal combustion engine, a

combustion cylinder, two scavenging fluid passages ending each per se in an opening in one half of said cylinder and disposed symmetrically one on each side of an axial centre plane through said cylinder half and directed towards said centre plane, a wall in each one of said passages radially confining the passage on its outside and extending substantially tangentially to the cylinder and making a sharp turn towards the central portion of the cylinder halt close to an axial confining edge of said pertaining opening, and a portion of said wall disposed adjacent the leading peripheral edge of the opening inclined an angle towards the cylinder axis decreasing towards said sharp turn, so that the scavenging fluid enteringthe opening is directed most axially in the cylinder in the vicinity of the sharp turn.

This arrangement of the scavenging passages has resulted in a very advantageous distribution and efiective filling of said cylinder half with scavenging fluid. In engines with doubleflow scavenging the combustion gases are then obviously at first displaced from saidcylinder hall and when said displacement is substantially finished and the scavenging fluid reaches the other cylinder end an extension of the scavenging fluid to the rest of the cylinder and a simultaneous displacement of the combustion gases from this part of the cylinder takes place. In engines filled substantially separately with scavenging fluid without any considerable mixture of scavenging fluid and combustion gases in one cylinder half with the scavenging'fluid and the combustion gases in the other cylinder half. The sharp turn of the outside walls of at least two scavenging fluid passages and the decreasing angle between portions of said walls near the leadin peripheral edge of the scavenging openings and the cylinder axis towards said sharp turn result g enging efllciency. However, the invention is not corporation of limited to a. scavenging process occurring in the manner herein described. One advantage of the invention is that a, large eflective scavenging opening area is obtained without reduction of the exhausttport area- In the accompanyin drawings some embodiments of the invention are illustrated by way of example, which, however, are by no means limiting for the invention, which may be employed in engines in which the scavenging fluid is air only or air admixed with the combustible.

Fig. 1 is a cross section of a cylinder of an engine with doubleflow scavenging the section-being taken through the scavenging and exhaust ports. Fig. 2 is a similar cross section of the cylinder half in which the scavenging openings are disposed of, a similar engine cylinder. Figs. 3, '4, 5 and 6 are partial axial sections of the engine cylinders according to Figs. 1 and 2 on go lines III-III, IV-IV, V-V and VI-VLrespeutively, in Figs. 1 and 2. Fig. 7 is a cross section of a cylinder of an engine with uniflow scavenging the section being taken through the scaven ing ports. Fig. 8 is a similar cross section through the scavenging openings in the cylinder of a further engine with uniflow scavenging. Figs. 9 and 10 are partial axial sections on lines IX- IX and X-X, respectively, in Figs. 7 and 8.

The engine cylinder 1 illustrated in cross section in Fig. l is intended for an engine with r with uniflow scavenging each cylinder half is I doubleflow scavenging through piston controlled scavenging and exhaust openings at one end of the working cylinder. The cross section is taken on a plane which in the lower end position of the piston touches the top of the piston and extends through the scavenging and exhaust openings. scavenging air is supplied to the working cylinder from one side ofthe engine through scavenging air supply passages 2, 3 one on each side of the cylinder and four scavenging air-passages l, 5, 6 and 1 leading to the cylinder hall which is hatched with dotted lines in Fig. l.

The passages 4, 5, Sand 1 are disposed symmetrically around the centre plane 8 of the hatched cylinder half. The passages 4 1 are inclined with'regard to the cylinder axisand direct the scavenging air entering the cylinder away from the top of the piston 9 controlling the scavenging openings as obvious from Figs. 3-6. Furthermore, the piston 9 is provided with a properly chamfered portion Ill. The engine cylinder I. is provided with a separate cylinder liner II. The exhaust passages I! extend from the not hatched cylinder half oi! Fig. 1. j i

The side of the scavenging passages 4 and Edisrial of the liner H.

- '3 posed nearest the intersection between the centre plane 8 and the periphery of the hatched cylinder half is confined radially by walls l3, H extending at first almost tangentially to the hatched cylinder half and making just before the axially extending inletedge of the pertaining scaven ing opening a sharp turn of about 90 forming surfaces l5, l directed parallel to the centre plane 8 as indicated by the line H. Said surfaces l5, l5 are formed completely in the mate- Portions l8, l8 of the wall l3 of the passage 4 nearest the leading peripheral edge of the scavenging opening are inclined an angle towards the cylinder axis which decreases as the wall it! approaches the sharp turn and the surface l5, as illustrated in Figs. 5 and 6. The symmetrically situated wall I4 .01 the passage 5 is formed in the same way as the wall 13. The radial depth of the passages 4 and 5 also' decreases towards the surfaces l5, l5 in the direction of the scavenging air flow, as illustrated in Figs. 5 and 6, resulting in an increased scavenging air velocity in this portion of the passages. This increased velocity together with the reduced angle between the wall portion [3 and the eviinder axis results in more axially directed air streams from the portion of the scavenging passages 4, 5 close to the sharp turn than from other portions of the passages, as indicated by the arrows and2i in Figs. 5 and 5.

'Ihescavenging air passages 5 and I are confined at the side nearest the intersection between the centre plane 8 and the periphery of the hatched cylinder half by walls 22, 23 extending at first substantially tangentially to the hatched cylinder half and making just before the axially extending inlet edge of the pertaining scavenging opening a sharp substantially 90 turn forming surfaces 24, directed towards the central cylinder portion, as indicated by the line 25. The wall 22 of the passage 5 has wall portions 21 and 28 close to the leading peripheral edge of the pertaining scavenging opening which, as obvious from Figs. 3 and 4, are inclined an angle towards the cylinder axis which decreases as the wall 22 approaches the sharp turn and the surface 24. The symmetrically situated passage 1 has a wall 23 shaped in the same way. Furthermore, as obvious from Figs. 3 and 4, the radial depth of the passages 5 and I decreases materially towards the surfaces 24, 25 in the direction of flow of the scavenging air. The describedarrangement results in an increased scav-.

enging air velocity in the passages 5, I. close to the surfaces 24, 25 and said velocity together with the reduced angleof inclination towards the cylinder axis of the wall portion 28 results in more axially directed air streams from the portions of the scavenging passages 5, I close to the sharp turn than from other portions, as indicated by the arrows 29 and 30 in Figs. 3 and 4.

The strong almost axial air streams obtained from the spaces just in front of the surfaces 15, I 5 and 24, 25 are apparently the cause of the important improvement of the scavenging efficiency observed during tests with the invention. At least partly, this appears to depend upon the fact that peripheral combustion gas whirls or congestions in the cylinder half, into which the scavenging air is admitted, are avoided.

Fig. 2 is a partial cross section of a cylinder of an engine with doubleflow scavenging according to a modification of the embodiment illustrated in Fig. 1 differing from said embodiment in a fewdetails only. The same reference nu merals as in Fig. 1 have therefore been used to indicate similar parts and the differing parts only are described hereinbelow. The difference consists in this that the walls I3, I 4 confining the passages 4 and 5 radially at the outside just before the axial inlet edge of the pertaining scavenging opening make a sharp turn forming surfaces 3|, 32 directed as indicated by the line 33 towards a point of the centre plane 8 situated on one third of the radius from the periphery of the cylinder. The walls 22,23 of the passages 5, I make a similar sharp turn as the corresponding walls in Fig. 1 forming surfaces 34 and 35 at the axial inlet edge of the pertain ing scavenging opening directed as indicated by the line 35 towards substantially the same portion of the centre plane 8 as the surfaces 3|, 32. Figs. 3-6 also illustrate partial axial sections of the passages 4 and 5 in Fig. 2.

Figs. 7 and 8 are cross sections of cylinders 31 and 38, respectively, of engines with uniflow scavenging from an inlet atone end of the working cylinder to an outlet at the'opposite end. In these embodiments scavenging air is supplied through scavenging air supply conduits 39, 45 and 4!, 42, respectively, at two sides of the engine cylinders. scavenging air is conducted from the scavenging air supply conduits 39, 40 through passages 43, 44, 45 and 45 to the hatched cylinder half in Fig. 7 symmetrically with reference to an axial centre plane 41 of said cylinder half. The passages 43-45 are directed away from the piston 48 controlling the scavenging openings. The piston may be chamfered correspondingly as indicated at 43 in Figs. 9 and 10. The outside walls, 50-53 of the passages 43-45 which are substantially tangential to the hatched cylinder half and situated nearest the intersection between the periphery of said cylinder half and the centre plane 41 make a sharp turn just before the axial inlet edge of the pertaining scavenging openings forming surfaces 545'| directed parallel with the centre plane and towards the central portion of the hatched cylinder half, respectively. The portions 58, 59 of the walls-50953- situated nearest the leading peripheral edge of the scavenging openings are inclined an angle towards the cylinder axis which decreases towards the surfaces 545'l as obvious from Figs. 9 and 10. The surfaces 54-51 are formed in the cylinder liner 50. In the vicinity of the surfaces 54'5l the air entering the cylinder is directed more axially than the air entering through the remaining portion of the pertaining scavenging opening, as previously described in connection with the embodiments according to Figs. 1 and 2.

The not hatched cylinder half in Fig. 7 is carried out as a converted image of the shaded cylinder half and is therefore not described in detail. Both cylinder halves operate with axial scavenging and to a large extent independently of each other so that the air and gases in one cylinder half do not mix with the air and gases of the other cylinder half during the scavenging period.

In the embodiment according to Fig. 8 the scavenging air supply conduit 4i is connected to four scavenging air passages 5|, 52, 53,54 deflecting the scavenging air and directed towards an axial centre plane .55 of the hatched cylinder half in Fig. 8. Walls 55-59 of the scavenging air passages 5l-54 situated nearest a sharp turn Just before the axial inlet edge of I the pertaining scavenging openings forming surfaces IO-l3 directed towards a portion of the centre plane 65 within the hatched cylinder half situated near the middle of the cylinder radius. The suriaces Ill-13 are formed in-the cylinder liner I4. The portions 58, 59, Figs. 9 and 10, of the walls 66-69 disposed nearest the leading peripheral edge of the scavenging openings are inclined an angle towards the cylinder axis which decreases towards the surfaces Ill-I3, respectively, so that in this case also strong axial air streams are obtained in the spaces near said surfaces. I

The not hatched cylinder half of Fig. 8 is carried out as a converted image of the hatched cylinder hall and is not described. The embodiments of the invention above described and illustrated in the drawings should only be considered as examples and the'invention may be modified in several'difierent ways within the following claims; For instance, the

ing isidirected most axially in the cylinder in the vicinity of the sharp turn. I

3. In a two stroke cycle internal combustion engine, a combustion cylinder, a working, piston in said cylinder, inlet openings in the cylinder controlledby said piston, two scavenging fluid passages .each ending in at least one of said open,

ings in one half of said cylinder and disposed symmetrically on each side of an axial center plane through said cylinder half and directed away from said piston towardssaid centre plane,

a. wall in'each one of said passages radially confining the passage on its outside and extending substantially tangentially to the cylinder and making a sharp turn close to theaxial confining edge of a pertaining opening nearest the intersection between the centre plane and the periphery of the cylinder half towards a portion number of scavenging air passages leading tothe 1 different cylinder halves may be larger or smaller than illustrated. The cylinders may furthermore be carriedout without separate liners.

What we claim is: I

1. In atwo stroke cycle internal combustion engine, a combustion cylinder, at least one working piston in said cylinder, inlet openings in the cylinder controlled by said piston, at least two scavenging fluid passages each ending in at least one of said openings in one half 01 said cylinder and disposed symmetrically on each side oian axial centre plane through said cylinder half and directed towards said centre plane, a wall in each one of said passages radially confining the passage on its outside andextending substantially tangentially to the cylinder and making a sharp turn towards the central portion of the cylinder half close to the axial confining edge of a pertaining opening, and a portion of said wall disposed adjacent the leading peripheral edge'of said opening inclined at an angle towards the cylinder axis decreasing towards said sharp turn, so that the scavenging fluid entering said opening is directed most axially in the cylinder in the vicinity of the sharp turn.

2. In a two stroke cycle internal combustion ,7

engine, a combustion cylinder, 9. working piston in said cylinder, inlet openings in the cylinder controlled by said piston, two scavenging fluid passages each ending in at least one of said open ings in one half of said cylinder and disposed symmetrically on each side of an axial centre plane through said cylinder half nearestthe intersec tion between said centre plane and the periphery of the cylinder half and directed away from the piston towards the centre plane, two further scavening fluid passages each ending in atleast one of the openings in the cylinder half and disposed symmetrically on each side of the axial centre plane second nearest said intersection and directed away from the piston towards the centre plane, a wall in each one of saidpassages radially confining the passage on its outside and extending substantially tangentially to. the cylin-' der and making a sharp turn towards the central portion of the cylinder half close to the axial I confining edge of a pertaining opening nearest the intersection, and a portion of said wall disposed adjacent the leading peripheral edge of of thecentre plane within the cylinder half between the cylinder .axis andtwo thirds of the radius from said axis, and a portion of said wall disposed adiacent the leading. peripheral edge of said opening inclined'at an angle towards the cylinder axis decreasing towards said sharp 1111,80 that the scavenging fluid entering said opening is directed most axially in the cylinder I and extending substantially tangentially to the cylinder and making a sharp turn towards the central portion of the cylinder half closeto the axial confining edge of a pertaining opening and formed in said liner at least after said sharp turn, and a portion of said wall disposed adjacent theleading peripheral edge of said opening inclined at an angle towards the cylinder axis decreasing towards the sharpv turn, so that the scav enging, fluid entering said opening is directed most axially m the cylinder in the vicinity of the sharp turn.;

5. In a two stroke cycle internal combustion engine, a combustion cylinder, two scavenging fluid passages each ending in an opening at one end of a first half of said cylinder and disposed symmetrically one on each side of an axial centre plane through said cylinder half and directed towards said centre plane, a wall in each one of said passages radially confining the passage on its I outside and extending substantially tangentially to the cylinder and making a sharp turn towards the central portion. of the cylinder halt/close to an axial confining edge of said pertaining opening, a portion of said wall disposed adjacent the leading peripheral edge of the opening inclined at an angle towards the cylinder axis decreasing towards said sharp turn, so that the scavenging fluid entering the opening is directed most axially I 3 in the cylinder in the vicinity of the sharp turn,

said opening inclined at an angle towards the cylinder axis decreasing towards said sharp turn,

so that the scavenging fluid entering said opena second cylinder half provided'with scavenging fluid passages formed as a mirror image of the first cylinderhalf, and an outlet at the opposite end of the combustion cylinder.

'6. In a two stroke cycle internal combustion -engine, a combustion cylinder, a reciprocating piston in said cylinder, two scavenging fluid passages each ending in an opening in one half of said cylinder controlled by said piston and disposed symmetrically one on each side of an axial centre plane through said cylinder half and dii rected away from the piston towards said centre plane, a wall in each one of said passages radially confining the passage'on its outside and extending substantially tangentially to the cylinder and making a sharp turn towards the central portion of the cylinder half close to an axial confining edge of the pertaining opening, and a portion of said wall disposed adjacent the leading peripheral edge of the opening inclined at an angle towards the cylinder axis decreasing towards said sharp turn, so that the scavenging fluid entering the opening is directed most axially in the cylinder in the vicinity of the sharp turn.

7. In a two stroke cycle internal combustion engine, a combustion cylinder, scavenging openings in one half of said cylinder, a reciprocating piston in the cylinder controlling said openings,

two scavenging fiuid passages each ending in a the other cylinder halt towards the centre plane.

a wall in each one 01' first-mentioned two passages radially confining the passage on its outside and extending substantially tangentially'to the cylinder and making a sharplturn towards the central portion of the cylinder close to an axial confining edge of the pertaining scavenging opening nearest the intersection, and a portion of said wall disposed adjacent the leading peripheral edge-of'the opening inclined at an angle towards the cylinder axis decreasing towards said sharp turn, so that the scavenging fluid enteringthe opening is directed most axially in the cylinder in the vicinity or the sharp turn.

HERMAN THEODOR'PYK. HILDING GUNNAR. CAMNER.

REFERENCES CITED The following references are of record in the 20 file of this patent:

UNITED STATES PATENTS Number Name Date 2,047,998 Dubois July 21, 1936 25 2,128,855 Schenker Aug. 30, 1938 2,228,832 Lieberherr Jan. 14, 1941 2,349,305 Pyk ,May 23, 1944' FOREIGN PATENTS 7 Number Country Date v 514,794 England 1939 England 1939 

